1. Field of the Invention
This invention relates to an optical device of the multilayer type including an anisotropic layer containing anlsotropic molecules, and an alignment layer which is disposed adjacent the anisotropic layer and which serves to align the anisotropic molecules in an adjacent surface region of the anisotropic layer.
2. Description of the Related Art
It is well known to provide an alignment layer for aligning anisotroplc molecules in an adjacent surface region of an anisotropic layer, e.g. liquid crystal molecules in a liquid crystal layer. Such an alignment layer is very often made from polyimide which requires a high temperature bake for a few hours and a number of rubs with a soft pile cloth. Long, high temperature bakes may adversely affect layers below the alignment layer, and the rubbing may introduce dust and dirt into the device. Thus, it is advantageous to minimize the number of such alignment layers in a multi-layer optical device.
EP-A-0689084 discloses the use of a photosensitive material to form an alignment layer, such material being altered using polarized UV radiation to form an alignment layer in which the alignment direction is determined by the direction of polarization of the UV radiation. EP-A-0689084 discloses a number of optical devices in which one or more such alignment layers (or conventional alignment layers) are used to align liquid crystal molecules in an adjacent anisotropic layer variously to produce optical retardation, for example from uniaxial (non-twisted) and twisted or chiral bire-fringent structures.